Forms of rifaximin and uses thereof

ABSTRACT

The present invention relates to Rifaximin amorphous forms, to their use in medicinal preparations and to therapeutic methods using them.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/275,272, filed May 12, 2014, which is a continuation of U.S.application Ser. No. 14/031,731, filed on Sep. 19, 2013, which is acontinuation of U.S. application Ser. No. 13/644,241, filed on Oct. 3,2012, which is a continuation of U.S. application Ser. No. 13/368,917,filed on Feb. 8, 2012, which is a continuation of U.S. application Ser.No. 13/165,410, filed on Jun. 21, 2011, which is a continuation of U.S.application Ser. No. 12/676,756, filed on Mar. 5, 2010, which is acontinuation-in-part of PCT/US2009/035192, filed Feb. 25, 2009, whichclaims the benefit of U.S. Provisional Application No. 61/031,329, filedFeb. 25, 2008. The entire contents of each of these applications areexpressly incorporated herein by reference.

BACKGROUND

Rifaximin (INN; see The Merck Index, XIII Ed., 8304) is an antibioticbelonging to the rifamycin class of antibiotics, e.g., a pyrido-imidazorifamycin. Rifaximin exerts its broad antibacterial activity, forexample, in the gastrointestinal tract against localizedgastrointestinal bacteria that cause infectious diarrhea, irritablebowel syndrome, small intestinal bacterial overgrowth, Crohn's disease,and/or pancreatic insufficiency. It has been reported that rifaximin ischaracterized by a negligible systemic absorption, due to its chemicaland physical characteristics (Descombe J. J. et al. Pharmacokineticstudy of rifaximin after oral administration in healthy volunteers. IntJ Clin Pharmacol Res, 14 (2), 51-56, (1994)).

Rifaximin is described in Italian Patent IT 1154655 and EP 0161534, bothof which are incorporated herein by reference in their entirety for allpurposes. EP 0161534 discloses a process for rifaximin production usingrifamycin O as the starting material (The Merck Index, XIII Ed., 8301).U.S. Pat. No. 7,045,620 B1 and PCT Publication WO 2006/094662 A1disclose polymorphic forms of rifaximin.

Rifaximin is approved for the treatment of pathologies caused bynon-invasive strains of Escherichia coli, a micro-organism which is notable to penetrate into GI mucosa and therefore remains in contact withgastrointestinal fluids.

SUMMARY

Described herein are polymorphic and amorphous forms of rifaximin notpreviously described. Form Amorphous forms of rifaximin are describedherein.

According to one aspect, a polymorph amorphous forms exhibits an X-raypowder diffraction pattern having characteristic peaks expressed indegrees 2θ (+/−0.20 degree θ) at 7.3 (approximate halo maximum),11.3-17.8 (amorphous halo range), and 15.8 (approximate halo maximum)degrees 2-θ; or 5.1-10.1 (amorphous halo range), 11.3-17.8 (amorphoushalo range), and 15.8 (approximate halo maximum) degrees 2-θ; or5.1-10.1 (amorphous halo range), 7.3 (approximate halo maximum), and11.3-17.8 (amorphous halo range) degrees 2-θ; or 5.1-10.1 (amorphoushalo range), 7.3 (approximate halo maximum), and 15.8 (approximate halomaximum) degrees 2-θ; or 5.1-10.1 (amorphous halo range), 7.3(approximate halo maximum), 11.3-17.8 (amorphous halo range), 15.8(approximate halo maximum) degrees 2-θ.

According to one aspect, a polymorph amorphous forms exhibits an X-raypowder diffraction pattern having characteristic peaks expressed indegrees 2θ (+/−0.20 degree θ) at 7.3 (approximate halo maximum),11.3-17.8 (amorphous halo range), and 15.8 (approximate halo maximum)degrees 2-θ.

According to one aspect, a polymorph amorphous forms exhibits an X-raypowder diffraction pattern having characteristic peaks expressed indegrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range),11.3-17.8 (amorphous halo range), and 15.8 (approximate halo maximum)degrees 2-θ.

According to one aspect, a polymorph amorphous forms exhibits an X-raypowder diffraction pattern having characteristic peaks expressed indegrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 7.3(approximate halo maximum), and 11.3-17.8 (amorphous halo range) degrees2-θ.

According to one aspect, a polymorph amorphous forms exhibits an X-raypowder diffraction pattern having characteristic peaks expressed indegrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 7.3(approximate halo maximum), and 15.8 (approximate halo maximum) degrees2-θ.

According to one aspect, a polymorph amorphous forms exhibits an X-raypowder diffraction pattern having characteristic peaks expressed indegrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 7.3(approximate halo maximum), 11.3-17.8 (amorphous halo range), 15.8(approximate halo maximum) degrees 2-θ.

In one embodiment, the amorphous forms exhibits thermogravimetricanalyses (TGA) of a 1.5% weight loss at 100° C.

In one embodiment, the polymorph exhibits Differential Scanningcalorimetry (DSC) of a broad endotherm at about 78° C. and a minorendotherm at 203° C.

In one embodiment, polymorph amorphous forms exhibits ModulatedDifferential Scanning calorimetry (MDSC) shows a glass transition (Tg)temperature onset to be about 199° C.

In one embodiment, the composition further comprises one or morepharmaceutically acceptable excipients. The excipients may be one ormore of a diluting agent, binding agent, lubricating agent,disintegrating agent, coloring agent, flavoring agent or sweeteningagent.

According to one embodiment, the pharmaceutical composition may beformulated as coated or uncoated tablets, hard or soft gelatin capsules,sugar-coated pills, lozenges, wafer sheets, pellets or powders in asealed packet. In a related embodiment, the pharmaceutical compositionmay also be formulated for topical use.

According to another aspect, provided herein are methods of treating,preventing or alleviating a bowel related disorder comprisingadministering to a subject in need thereof an effective amount ofamorphous form of rifaximin.

In one embodiment, the subject is suffering from at least one bowelrelated disorder selected from the group consisting of irritable bowelsyndrome, travelers' diarrhea, small intestinal bacterial overgrowth,Crohn's disease, chronic pancreatitis, pancreatic insufficiency,enteritis and colitis.

In another embodiment, the EtOH slurry comprises an EtOH/H₂O slurry inthe ratio of from between 1 to 0.02-0.45.

Provided herein, according to one aspect, are processes for producing amixture of polymorphs ζ and γ comprising humidifying Form ζ.

Provided herein, according to one aspect, are processes for producingamorphous rifaximin comprising grinding Form γ or a mixture of Form γand Form η of rifaximin.

According to one aspect, provided herein are processes for producingamorphous rifaximin comprising crash precipitation from ethyl acetatewith heptane.

In one embodiment, the process further comprises milling the producedamorphous rifaximin.

According to one aspect, provided herein are processes for producingamorphous rifaximin comprising lyophilization in p-dioxane:water 1:1,and fast evaporation from acetone.

In one embodiment, the process further comprises milling the producedamorphous rifaximin.

According to one aspect, provided herein are processes for producingamorphous rifaximin comprising precipitation from acetone.

In one embodiment, the process further comprises milling the producedamorphous rifaximin.

According to one aspect, provided herein are processes for producingamorphous rifaximin comprising precipitating the initial rifaximin formsin the manner set forth in Table 7.

According to one aspect, provided herein are processes for producingamorphous Form of rifaximin comprising precipitating the initial formsin the manner set forth in Tables 20-22.

Provided herein, according to one aspect, are kits for treating a boweldisorder in a subject, comprising amorphous form of rifaximin andinstructions for use.

Provided herein, according to one aspect, are packaged compositionscomprising, a therapeutically effective amount of amorphous form ofrifaximin and a pharmaceutically acceptable carrier or diluent, whereinthe composition is formulated for treating a subject suffering from orsusceptible to a bowel disorder, and packaged with instructions to treata subject suffering from or susceptible to a bowel disorder.

In one aspect, a pharmaceutical composition is presented, whichcomprises amorphous form of rifaximin and a pharmaceutically acceptablecarrier.

In one embodiment, the pharmaceutical composition further comprisesexcipients.

According to another embodiment, the excipients are one or more of adiluting agent, binding agent, lubricating agent, disintegrating agent,coloring agent, flavoring agent or sweetening agent.

In another embodiment, the composition is formulated for selected coatedand uncoated tablets, hard and soft gelatine capsules, sugar-coatedpills, lozenges, wafer sheets, pellets and powders in sealed packets.

In one embodiment, the composition is formulated for topical use.

Presented herein, according to one aspect, are methods of treating,preventing, or alleviating a bowel related disorder comprisingadministering to a subject in need thereof a cell infected with a viruswith an effective amount of amorphous form of rifaximin.

According to another embodiment, wherein the bowel related disorder isone or more of irritable bowel syndrome, travelers' diarrhea, smallintestinal bacterial overgrowth, Crohn's disease, chronic pancreatitis,pancreatic insufficiency, or colitis.

Presented herein, according to one aspect, are methods of assessing theefficacy of a bowel related disorder treatment in a subject, monitoringthe progress of a subject being treated for a bowel related disorder, ora method of selecting a subject for treatment of a bowel disorder,comprising:

determining a pre-treatment level of bacterial overgrowth;

administering a therapeutically effective amount of amorphous form ofrifaximin to the subject; and determining a post-treatment level ofbacterial overgrowth after an initial period of treatment with theamorphous form of rifaximin.

In one embodiment, the modulation of the level of bacterial overgrowthindicates efficacy of the treatment.

In another embodiment, a decrease in bacterial overgrowth indicates thatthe treatment is efficacious.

In another embodiment, the modulation of the bacterial overgrowth is anindication that the subject is likely to have a favorable clinicalresponse to the treatment.

Presented herein, according to one aspect, are kits for treating a boweldisorder in a subject, comprising one or more actions for use.

Also presented herein, according to one aspect are packaged compositionscomprising a therapeutically effective amount of amorphous form ofrifaximin and a pharmaceutically acceptable carrier or diluents, whereinthe composition is formulated for treating a subject suffering from orsusceptible to a bowel disorder, and packaged with instructions to treata subject suffering from or susceptible to a bowel disorder.

Also presented herein is the use of one or more amorphous forms ofrifaximin as a medicament.

Presented herein, according to another aspect, are processes for theproduction of one amorphous form of rifaximin.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising an XRPD pattern substantially similar to FIG. 1.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a TGA and a DSC substantially similar to FIG. 2.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising an XRPD pattern substantially similar to FIG. 4.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a DSC substantially similar to FIG. 6.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a cycling DSC substantially similar to FIG. 7.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a TG substantially similar to FIG. 8.

Presented herein, according to another aspect, is an amorphous Form ofrifaximin comprising a cycling DSC substantially similar to FIG. 10.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a TG substantially similar to FIG. 11.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a cycling DSC substantially similar to FIG. 13.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a TG substantially similar to FIG. 14.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a modulated DSC substantially similar to FIG. 15.

Presented herein, according to another aspect, is a Form amorphous ofrifaximin comprising a modulated DSC substantially similar to FIG. 16.

Other embodiment and aspects are disclosed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary XRPD pattern of rifaximin form amorphous.

FIG. 2 shows an exemplary TGA and a DSC of rifaximin form amorphous.

FIG. 3 shows an exemplary MDSC of rifaximin form amorphous.

FIG. 4 depicts an exemplary XRPD pattern of rifaximin form amorphous.

FIG. 5 depicts an exemplary XRPD overlay of rifaximin amorphousattempts.

FIG. 6 depicts an exemplary DSC of rifaximin, amorphous (crashprecipitation from ethyl acetate with heptane).

FIG. 7 depicts exemplary results of cycling DSC of rifaximin, amorphous(crash precipitation from ethyl acetate with heptane).

FIG. 8 depicts exemplary results of TG of rifaximin, amorphous (crashprecipitation from ethyl acetate with heptane).

FIG. 9 depicts an exemplary XRPD overlay of rifaximin, amorphous (top tobottom):amorphous (crash precipitation from ethyl acetate with heptane)and likely amorphous.

FIG. 10 depicts exemplary results of cycling DSC of rifaximin, amorphous(lyophilization in p-dioxane:water 1:1).

FIG. 11 depicts an exemplary results of TG of rifaximin, amorphous(lyophilization in p-dioxane:water 1:1).

FIG. 12 depicts an exemplary XRPD of Rifaximin, amorphous (top tobottom):amorphous (lyophilization in p-dioxane:water 1:1) and likelyamorphous.

FIG. 13 depicts exemplary results of cycling DSC of rifaximin, amorphous(fast evaporation from acetone).

FIG. 14 depicts exemplary results of TG of rifaximin, amorphous (fastevaporation from acetone).

FIG. 15 depicts exemplary results of modulated DSC of rifaximin,amorphous (crash precipitation from ethyl acetate with heptane).

FIG. 16 depicts exemplary results of modulated DSC of rifaximin,amorphous (crash precipitation from ethyl acetate with heptane).

DETAILED DESCRIPTION

Embodiments of the invention relate to the discovery of new polymorphicforms of rifaximin and the use of those forms as antibiotics. In oneembodiment the use of amorphous forms (FIGS. 1-3, 4, and 5-16) of theantibiotic known as Rifaximin (INN), in the manufacture of medicinalpreparations for the oral or topical route is contemplated. Embodimentsof the invention also relate to administration of such medicinalpreparations to a subject in need of treatment with antibiotics.

Rifaximin is a compound of the rifamycin class of antibiotics. Rifaximinis a compound having the structure of Formula I:

As used herein, “rifaximin Form ζ,” “Form ζ” “Form ζ of rifaximin,”“polymorph ζ,” and “rifaximin ζ” are used interchangeably to denote thepolymorphic form of rifaximin as further described herein by, forexample, one or more peaks of an x-ray diffractogram, differentialscanning calorimetry data. Form ζ comprises an x-ray powder diffractionpattern peak positions at about 4.7 (doublet), 7.6 (doublet), and 9.5degrees 2-θ; or at about 4.7 (doublet), 7.3, and 8.2 degrees 2-θ; or atabout 7.6 (doublet), 8.6, and 10.5 degrees 2-θ; or at about 8.2, 8.6,and 9.5 degrees 2-θ; or at about 10.2 (triplet), 12.6 (quintet), and13.2 (doublet) degrees 2-θ; or at about 7.3, 10.5, and 12.9 (doublet)degrees 2-θ; or at about 7.3, 7.6 (doublet), 8.2, 8.6 degrees 2-θ; or atabout 4.7 (doublet), 7.3, 7.6 (doublet), 9.5, and 10.5 degrees 2-θ; orat about 8.2, 8.6, 9.5, 10.2 (triplet), and 10.5 degrees 2-θ; or atabout 8.6, 9.5, 10.2 (triplet), 10.5, and 11.2 (doublet) degrees 2-θ; orat about 4.7 (doublet), 6.3, 6.4, 7.3, 7.6 (doublet), 8.2, 8.6, 9.5,10.2 (triplet), 10.5, 11.2 (doublet), 11.9 (doublet), 12.2 (weak), 12.6(quintet), 12.9 (doublet), 13.2 (doublet) degrees 2-θ. Form ζ may beidentified and characterized by one or more of these parameters and/orone or more of the peaks or points in the ranges.

As used herein, “rifaximin Form η,” “Form η,” “polymorph” “Form η ofrifaximin” and “rifaximin η” are used interchangeably to denote thepolymorphic form of rifaximin as further described herein by, forexample, one or more peaks of an x-ray diffractogram and methods ofmaking such form. Form η comprises x-ray powder diffraction pattern peakpositions at about 6.1, 7.3, and 7.5 degrees 2-θ; or 6.1, 7.3, and 7.9degrees 2-θ; or 6.1, 7.3, and 8.8 degrees 2-θ; or 6.1, 7.3, and 12.7degrees 2-θ; or 6.1, 7.5, and 8.8 degrees 2-θ; or 6.1, 7.5, and 7.9degrees 2-θ; or 5.3, 6.1, and 7.3 degrees 2-θ; or 5.3, 6.1, and 7.9degrees 2-θ; or 5.3, 6.1, and 12.7 degrees 2-θ; or 5.3, 6.1, and 7.5degrees 2-θ; or 5.3, 6.1, and 8.8 degrees 2-θ; or 6.1, 7.3, 7.5, 7.9,8.8, and 12.7 degrees 2-θ; or 5.3, 6.1, 7.3, 7.5, 7.9, 8.8, 12.7 degrees2-θ; or 5.3, 6.1, 7.3, 7.9, 8.8, and 12.7 degrees 2-θ; or 5.3, 6.1, 7.3,7.5, 8.8, and 12.7 degrees 2-θ; or 5.3, 6.1, 7.3, 7.5, 7.9, 8.8, and12.7 degrees 2-θ. Form η may be identified and characterized by one ormore of these parameters and/or one or more of the peaks or points inthe ranges.

As used herein, “rifaximin Form τ,” “Form τ,” “polymorph τ,” “Form τ ofrifaximin” and “rifaximin t” are used interchangeably to denote thepolymorphic form of rifaximin as further described herein by, forexample, one or more peaks of an x-ray diffractogram, NMR, thermal data,or hot stage microscopy and methods of making such form. Form τcomprises x-ray powder diffraction pattern peak positions describedabove. Form τ may be identified and characterized by one or more ofthese parameters and/or one or more of the peaks or points in theranges.

As used herein, “rifaximin mesylate Form,” “Form meslate,” “polymorphmesylate,” “Form mesylate of rifaximin” and “rifaximin mesylate” areused interchangeably to denote the polymorphic form of rifaximin asfurther described herein by, for example, one or more peaks of an x-raydiffractogram and methods of making such form. Mesylate Form comprisesx-ray powder diffraction pattern peak positions described above.Mesylate Form may be identified and characterized by one or more ofthese parameters and/or one or more of the peaks or points in theranges.

As used herein, “rifaximin Form amorphous,” “Form amorphous,” and“rifaximin amorphous” are used interchangeably to denote the amorphousforms of rifaximin formed from mechanical disruption of polymorphicforms of rifaximin as further described herein by, for example, one ormore peaks of an x-ray diffractogram, including 7.3 (approximate halomaximum), 11.3-17.8 (amorphous halo range), and 15.8 (approximate halomaximum) degrees 2-θ; or 5.1-10.1 (amorphous halo range), 11.3-17.8(amorphous halo range), and 15.8 (approximate halo maximum) degrees 2-θ;or 5.1-10.1 (amorphous halo range), 7.3 (approximate halo maximum), and11.3-17.8 (amorphous halo range) degrees 2-θ; or 5.1-10.1 (amorphoushalo range), 7.3 (approximate halo maximum), and 15.8 (approximate halomaximum) degrees 2-θ; or 5.1-10.1 (amorphous halo range), 7.3(approximate halo maximum), 11.3-17.8 (amorphous halo range), 15.8(approximate halo maximum) degrees 2-θ; (FIG. 1) dissolution, ordifferential scanning calorimetry data (FIG. 2), Form amorphous may beidentified and characterized by one or more of these parameters and/orone or more of the peaks or points in the ranges. The amorphous form, asused herein, is encompassed by the general reference to rifaximinpolymorphs or polymorphic forms of rifaximin. The amorphous forms may beidentified, for example, by XRPD, TG, DSC, modulated DSC, or FT-IRmethods (FIGS. 1-4).

As used herein, the term polymorph is occasionally used as a generalterm in reference to the forms of rifaximin and includes within thecontext, salt, hydrate, polymorph and amorphous forms of rifaximindisclosed herein. This use depends on context and will be clear to oneof skill in the art.

As used herein, the term “about” when used in reference to x-ray powderdiffraction pattern peak positions refers to the inherent variability ofthe peaks depending on, for example, the calibration of the equipmentused, the process used to produce the polymorph, the age of thecrystallized material and the like, depending on the instrumentationused. In this case the measure variability of the instrument was about+0.2 degrees 2-θ. A person skilled in the art, having the benefit ofthis disclosure, would understand the use of “about” in this context.The term “about” in reference to other defined parameters, e.g., watercontent, C_(max), t_(max), AUC, intrinsic dissolution rates,temperature, and time, indicates the inherent variability in, forexample, measuring the parameter or achieving the parameter. A personskilled in the art, having the benefit of this disclosure, wouldunderstand the variability of a parameter as connoted by the use of theword about.

Polymorphism, as used herein, refers to the occurrence of differentcrystalline forms of a single compound in distinct hydrate status, e.g.,a property of some compounds and complexes. Thus, polymorphs aredistinct solids sharing the same molecular formula, yet each polymorphmay have distinct physical properties. Therefore, a single compound maygive rise to a variety of polymorphic forms where each form hasdifferent and distinct physical properties, such as solubility profiles,melting point temperatures, hygroscopicity, particle shape, density,flowability, compactibility and/or x-ray diffraction peaks. Thesolubility of each polymorph may vary, thus, identifying the existenceof pharmaceutical polymorphs is essential for providing pharmaceuticalswith predictable solubility profiles. It is desirable to investigate allsolid state forms of a drug, including all polymorphic forms, and todetermine the stability, dissolution and flow properties of eachpolymorphic form. Polymorphic forms of a compound can be distinguishedin a laboratory by X-ray diffraction spectroscopy and by other methodssuch as, infrared spectrometry. For a general review of polymorphs andthe pharmaceutical applications of polymorphs see G. M. Wall, PharmManuf. 3, 33 (1986); J. K. Haleblian and W. McCrone, J Pharm. Sci., 58,911 (1969); and J. K. Haleblian, J. Pharm. Sci., 64, 1269 (1975), all ofwhich are incorporated herein by reference.

As used herein, “subject” includes organisms which are capable ofsuffering from a bowel disorder or other disorder treatable by rifaximinor who could otherwise benefit from the administration of a rifaximin asdescribed herein, such as human and non-human animals. Preferred humananimals include human subjects. The term “non-human animals” of theinvention includes all vertebrates, e.g., mammals, e.g., rodents, e.g.,mice, and non-mammals, such as non-human primates, e.g., sheep, dog,cow, chickens, amphibians, reptiles, etc. Susceptible to a boweldisorder is meant to include subjects at risk of developing a boweldisorder infection, i.e., subjects suffering from immune suppression,subjects that have been exposed to other subjects with a bacterialinfection, physicians, nurses, subjects traveling to remote areas knownto harbor bacteria that causes travelers' diarrhea, etc.

The language “a prophylactically effective amount” of a compound refersto an amount of a compound of the invention of formula (I) or otherwisedescribed herein which is effective, upon single or multiple doseadministration to the subject, in preventing or treating a bacterialinfection.

The language “therapeutically effective amount” of a compound of theinvention refers to an amount of an agent which is effective, uponsingle or multiple dose administration to the subject to provide atherapeutic benefit to the subject. In one embodiment, the therapeuticbenefit is inhibiting a virus, or in prolonging the survivability of asubject with such a viral infection. In another embodiment, thetherapeutic benefit is inhibiting a bacterial infection or prolongingthe survival of a subject with such a bacterial infection beyond thatexpected in the absence of such treatment.

Rifaximin exerts a broad antibacterial activity in the gastrointestinaltract against localized gastrointestinal bacteria that cause infectiousdiarrhea, including anaerobic strains. It has been reported thatrifaximin is characterized by a negligible systemic absorption, due toits chemical and physical characteristics (Descombe J. J. et al.Pharmacokinetic study of rifaximin after oral administration in healthyvolunteers. Int J Clin Pharmacol Res, 14 (2), 51-56, (1994)).

In respect to possible adverse events coupled to the therapeutic use ofrifaximin, the induction of bacterial resistance to the antibiotics isof particular relevance.

From this point of view, any differences found in the systemicabsorption of ζ, η or amorphous forms of rifaximin may be significant,because at sub-inhibitory concentration of rifaximin, such as in therange from 0.1 to 1 μg/ml, selection of resistant mutants has beendemonstrated to be possible (Marchese A. et al. In vitro activity ofrifaximin, metronidazole and vancomycin against clostridium difficileand the rate of selection of spontaneously resistant mutants againstrepresentative anaerobic and aerobic bacteria, including ammoniaproducing species. Chemotherapy, 46(4), 253-266, (2000)).

Polymorphs of rifaximin have been found to have differing in vivobioavailability properties. Thus, the polymorphs disclosed herein wouldbe useful in the preparation of pharmaceuticals with differentcharacteristics for the treatment of infections. This would allowgeneration of rifaximin preparations that have significantly differentlevels of adsorption with C_(max) values from about 0.0 ng/ml to 5.0μg/ml. This leads to preparation of rifaximin compositions that are fromnegligibly to significantly adsorbed by subjects undergoing treatment.One embodiment of the invention is modulating the therapeutic action ofrifaximin by selecting the proper polymorphic form, or mixture of forms,for treatment of a patient. For example, in the case of invasivebacteria, the most bioavailable polymorphic form can be selected fromthose disclosed herein, whereas in case of non-invasive pathogens lessadsorbed forms of rifaximin can be selected, since they may be safer forthe subject undergoing treatment.

The above-mentioned amorphous forms can be advantageously used as pureand homogeneous products in the manufacture of medicinal preparationscontaining rifaximin.

Some features of a rifaximin amorphous forms include, for example:

Amorphous rifaximin (FIGS. 1-3) was prepared by milling Form γ or Formγ+η at ambient temperature. Amorphous rifaximin was physically stableunder various relative humidities and exhibited a high glass transitiontemperature onset of 199° C.

For XRPD analysis, accuracy and precision associated with third partymeasurements on independently prepared samples on different instrumentsmay lead to variability which is greater than ±0.1° 2θ. For d-spacelistings, the wavelength used to calculate d-spacings was 1.541874 Å, aweighted average of the Cu—Kα1 and Cu—Kα2 wavelengths. Variabilityassociated with d-spacing estimates was calculated from the USPrecommendation, at each d-spacing, and provided in the respective datatables and peak lists.

Thermogravimetry (TG) analysis of amorphous rifaximin demonstrated a1.5% weight loss to 100° C., accompanied by a broad endotherm at 78° C.in the DSC trace, indicating the material contained residual solvent. Aminor endotherm at 203° C. was also observed in the DSC trace. CyclicDSC was performed to dry the sample and determine the T_(g), however theglass transition temperature was not apparent from the data. Modulateddifferential scanning calorimetry showed the glass transition (T_(g))temperature onset to be approximately 199° C. (FIG. 2). Amorphousrifaximin was hygroscopic gaining 11.6% weight under 95% RH. The gainedweight was lost during the desorption cycle. The post moisture balanceXRPD pattern was amorphous.

The behavior of amorphous rifaximin under various relative humiditieswas also investigated. Amorphous material was stored under 43% RH for 5days, 58% RH for 8 days and 75% RH for 2 days. The material remainedamorphous by XRPD analysis.

Amorphous rifaximin may also be obtained by spray-drying, fluid bed andball mill crushing as further described below.

Methods of Treatment

Provided herein are methods of treating, preventing, or alleviatingbowel related disorders comprising administering to a subject in needthereof an effective amount of amorphous form polymorph of rifaximin.Bowel related disorders include one or more of irritable bowel syndrome,diarrhea, microbe associated diarrhea, Clostridium difficile associateddiarrhea, travelers' diarrhea, small intestinal bacterial overgrowth,Crohn's disease, chronic pancreatitis, pancreatic insufficiency,enteritis, colitis, hepatic encephalopathy, or pouchitis.

The length of treatment for a particular bowel disorder will depend inpart on the disorder. For example, travelers' diarrhea may only requiretreatment duration of 12 to about 72 hours, while Crohn's disease mayrequire treatment durations from about 2 days to 3 months. Dosages ofrifaximin will also vary depending on the diseases state. Proper dosageranges are provided herein infra.

Provided herein are methods of treating or preventing a pathology in asubject suspected of being exposed to a biological warfare agent.

The identification of those subjects who are in need of prophylactictreatment for bowel disorder is well within the ability and knowledge ofone skilled in the art. Certain of the methods for identification ofsubjects which are at risk of developing a bowel disorder which can betreated by the subject method are appreciated in the medical arts, suchas family history, travel history and expected travel plans, thepresence of risk factors associated with the development of that diseasestate in the subject. A clinician skilled in the art can readilyidentify such candidate subjects, by the use of, for example, clinicaltests, physical examination and medical/family/travel history.

A method of assessing the efficacy of the treatment in a subjectincludes determining the pre-treatment level of intestinal bacterialovergrowth by methods well known in the art (e.g., hydrogen breathtesting, biopsy, sampling of the intestinal bacteria, etc.) and thenadministering a therapeutically effective amount of a rifaximinpolymorph to the subject. After an appropriate period of time (e.g.,after an initial period of treatment) from the administration of thecompound, e.g., 2 hours, 4 hours, 8 hours, 12 hours, or 72 hours, thelevel of bacterial overgrowth is determined again. The modulation of thebacterial level indicates efficacy of the treatment. The level ofbacterial overgrowth may be determined periodically throughouttreatment. For example, the bacterial overgrowth may be checked everyfew hours, days or weeks to assess the further efficacy of thetreatment. A decrease in bacterial overgrowth indicates that thetreatment is efficacious. The method described may be used to screen orselect subjects that may benefit from treatment with a rifaximinpolymorph.

In yet another aspect, a method of treating a subject suffering from orsusceptible to a bowel disorder comprises administering to a subject inneed thereof a therapeutically effective amount of a rifaximin polymorphdescribed herein, to thereby treat the subject. Upon identification of asubject suffering from or susceptible to a bowel disorder, for example,IBS, one or more rifaximin polymorphs are administered.

In one aspect, methods of assessing the efficacy of treatment with arifaximin polymorph in a subject comprise determining the pre-treatmentlevel of bacterial overgrowth, administering a therapeutically effectiveamount of a rifaximin polymorph to the subject, and determining thebacterial overgrowth after an initial period of treatment with arifaximin polymorph, wherein the modulation of the bacterial overgrowthindicates efficacy of an anti-bacterial treatment.

Efficacy of a treatment may be measured for example, as reduction ofbacterial overgrowth. Efficacy may also be measured in terms of areduction of symptoms associated with the bowel disorder, astabilization of symptoms, or a cessation of symptoms associated with abowel disorder, for example, a reduction of nausea, bloating, diarrhea,and the like.

In one aspect, methods of monitoring the progress of a subject beingtreated with a rifaximin polymorph comprise determining thepre-treatment level of bacterial overgrowth, administering atherapeutically effective amount of a rifaximin polymorph to thesubject, and determining the bacterial overgrowth after an initialperiod of treatment with a rifaximin polymorph, wherein the modulationof the bacterial overgrowth indicates efficacy of an antibacterialtreatment.

Pharmaceutical Preparations

Embodiments also provide pharmaceutical compositions, comprising aneffective amount of a rifaximin polymorph (e.g., Form ζ, Form η, Formα-dry, Form τ, Form β-1, Form β-2, Form ε-dry, mesylate Form oramorphous forms) described herein and a pharmaceutically acceptablecarrier. In a further embodiment, the effective amount is effective totreat a bacterial infection, e.g., small intestinal bacterialovergrowth, Crohn's disease, hepatic encephalopathy, antibioticassociated colitis, and/or diverticular disease.

For examples of the use of rifaximin to treat Travelers' diarrhea, seeInfante R M, Ericsson C D, Zhi-Dong J, Ke S, Steffen R, Riopel L, Sack DA, DuPont, HL. Enteroaggregative Escherichia coli Diarrhea in Travelers:Response to Rifaximin Therapy. Clinical Gastroenterology and Hepatology.2004; 2:135-138; and Steffen R, M. D., Sack D A, M. D., Riopel L, Ph.D.,Zhi-Dong J, Ph.D., Sturchler M, M. D., Ericsson C D, M. D., Lowe B, M.Phil., Waiyaki P, Ph.D., White M, Ph.D., DuPont H L, M. D. Therapy ofTravelers' Diarrhea With Rifaximin on Various Continents. The AmericanJournal of Gastroenterology. May 2003, Volume 98, Number 5, all of whichare incorporated herein by reference in their entirety.

Embodiments also provide pharmaceutical compositions comprising one ormore of a Form ζ, Form η, Form α-dry, Form τ, Form β-1, Form β-2, Formε-dry, mesylate Form or amorphous forms of rifaximin and apharmaceutically acceptable carrier. That is, formulations may containonly one polymorph or may contain a mixture of more than one polymorph.Mixtures may be selected, for example on the basis of desired amounts ofsystemic adsorption, dissolution profile, desired location in thedigestive tract to be treated, and the like. Embodiments of thepharmaceutical composition further comprise excipients, for example, oneor more of a diluting agent, binding agent, lubricating agent,disintegrating agent, coloring agent, flavoring agent or sweeteningagent. One composition may be formulated for selected coated anduncoated tablets, hard and soft gelatin capsules, sugar-coated pills,lozenges, wafer sheets, pellets and powders in sealed packet. Forexample, compositions may be formulated for topical use, for example,ointments, pomades, creams, gels and lotions.

In an embodiment, the rifaximin polymorph is administered to the subjectusing a pharmaceutically-acceptable formulation, e.g., apharmaceutically-acceptable formulation that provides sustained deliveryof the rifaximin polymorph to a subject for at least 12 hours, 24 hours,36 hours, 48 hours, one week, two weeks, three weeks, or four weeksafter the pharmaceutically-acceptable formulation is administered to thesubject.

In certain embodiments, these pharmaceutical compositions are suitablefor topical or oral administration to a subject. In other embodiments,as described in detail below, the pharmaceutical compositions of thepresent invention may be specially formulated for administration insolid or liquid form, including those adapted for the following: (1)oral administration, for example, drenches (aqueous or non-aqueoussolutions or suspensions), tablets, boluses, powders, granules, pastes;(2) parenteral administration, for example, by subcutaneous,intramuscular or intravenous injection as, for example, a sterilesolution or suspension; (3) topical application, for example, as acream, ointment or spray applied to the skin; (4) intravaginally orintrarectally, for example, as a pessary, cream or foam; or (5) aerosol,for example, as an aqueous aerosol, liposomal preparation or solidparticles containing the compound.

The phrase “pharmaceutically acceptable” refers to those rifaximinpolymorphs of the present invention, compositions containing suchcompounds, and/or dosage forms which are, within the scope of soundmedical judgment, suitable for use in contact with the tissues of humanbeings and animals without excessive toxicity, irritation, allergicresponse, or other problem or complication, commensurate with areasonable benefit/risk ratio.

The phrase “pharmaceutically-acceptable carrier” includespharmaceutically-acceptable material, composition or vehicle, such as aliquid or solid filler, diluent, excipient, solvent or encapsulatingmaterial, involved in carrying or transporting the subject chemical fromone organ, or portion of the body, to another organ, or portion of thebody. Each carrier is preferably “acceptable” in the sense of beingcompatible with the other ingredients of the formulation and notinjurious to the subject. Some examples of materials which can serve aspharmaceutically-acceptable carriers include: (1) sugars, such aslactose, glucose and sucrose; (2) starches, such as corn starch andpotato starch; (3) cellulose, and its derivatives, such as sodiumcarboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4)powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients,such as cocoa butter and suppository waxes; (9) oils, such as peanutoil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil andsoybean oil; (10) glycols, such as propylene glycol; (11) polyols, suchas glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters,such as ethyl oleate and ethyl laurate; (13) agar; (14) bufferingagents, such as magnesium hydroxide and aluminum hydroxide; (15) alginicacid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer'ssolution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21)other non-toxic compatible substances employed in pharmaceuticalformulations.

Wetting agents, emulsifiers and lubricants, such as sodium laurylsulfate and magnesium stearate, as well as coloring agents, releaseagents, coating agents, sweetening, flavoring and perfuming agents,preservatives and antioxidants can also be present in the compositions.

Examples of pharmaceutically-acceptable antioxidants include: (1) watersoluble antioxidants, such as ascorbic acid, cysteine hydrochloride,sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2)oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and (3) metal chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

Compositions containing a rifaximin forms disclosed herein include thosesuitable for oral, nasal, topical (including buccal and sublingual),rectal, vaginal, aerosol and/or parenteral administration. Thecompositions may conveniently be presented in unit dosage form and maybe prepared by any methods well known in the art of pharmacy. The amountof active ingredient which can be combined with a carrier material toproduce a single dosage form will vary depending upon the host beingtreated, the particular mode of administration. The amount of activeingredient which can be combined with a carrier material to produce asingle dosage form will generally be that amount of the compound whichproduces a therapeutic effect. Generally, out of one hundred %, thisamount will range from about 1% to about ninety-nine % of activeingredient, preferably from about 5% to about 70%, most preferably fromabout 10% to about 30%.

Methods of preparing these compositions include the step of bringinginto association a rifaximin polymorph(s) with the carrier and,optionally, one or more accessory ingredients. In general, theformulations are prepared by uniformly and intimately bringing intoassociation a rifaximin polymorph with liquid carriers, or finelydivided solid carriers, or both, and then, if necessary, shaping theproduct.

Compositions suitable for oral administration may be in the form ofcapsules, cachets, pills, tablets, lozenges (using a flavored basis,usually sucrose and acacia or tragacanth), powders, granules, or as asolution or a suspension in an aqueous or non-aqueous liquid, or as anoil-in-water or water-in-oil liquid emulsion, or as an elixir or syrup,or as pastilles (using an inert base, such as gelatin and glycerin, orsucrose and acacia) and/or as mouth washes and the like, each containinga predetermined amount of a rifaximin polymorph(s) as an activeingredient. A compound may also be administered as a bolus, electuary orpaste.

The amorphous form can be advantageously used in the production ofmedicinal preparations having antibiotic activity, containing rifaximin,for both oral and topical use. The medicinal preparations for oral usewill contain rifaximin amorphous form together with the usualexcipients, for example diluting agents such as mannitol, lactose andsorbitol; binding agents such as starches, gelatines, sugars, cellulosederivatives, natural gums and polyvinylpyrrolidone; lubricating agentssuch as talc, stearates, hydrogenated vegetable oils, polyethylenglycoland colloidal silicon dioxide; disintegrating agents such as starches,celluloses, alginates, gums and reticulated polymers; colouring,flavouring and sweetening agents.

Embodiments of the invention include solid preparations administrable bythe oral route, for instance coated and uncoated tablets, of soft andhard gelatin capsules, sugar-coated pills, lozenges, wafer sheets,pellets and powders in sealed packets or other containers.

Medicinal preparations for topical use can contain rifaximin amorphousforms together with usual excipients, such as white petrolatum, whitewax, lanoline and derivatives thereof, stearylic alcohol, propyleneglycol, sodium lauryl sulfate, ethers of fatty polyoxyethylene alcohols,esters of fatty polyoxyethylene acids, sorbitan monostearate, glycerylmonostearate, propylene glycol monostearate, polyethylene glycols,methylcellulose, hydroxymethyl propylcellulose, sodiumcarboxymethylcellulose, colloidal aluminum and magnesium silicate,sodium alginate.

Embodiments of the invention relate to all of the topical preparations,for instance ointments, pomades, creams, gels and lotions.

In solid dosage forms of rifaximin for oral administration (capsules,tablets, pills, dragees, powders, granules and the like), the activeingredient is typically mixed with one or morepharmaceutically-acceptable carriers, such as sodium citrate ordicalcium phosphate, and/or any of the following: (1) fillers orextenders, such as starches, lactose, sucrose, glucose, mannitol, and/orsilicic acid; (2) binders, such as, for example, carboxymethylcellulose,alginates, gelatin, polyvinyl pyrrolidone, sucrose and/or acacia; (3)humectants, such as glycerol; (4) disintegrating agents, such asagar-agar, calcium carbonate, potato or tapioca starch, alginic acid,certain silicates, and sodium carbonate; (5) solution retarding agents,such as paraffin; (6) absorption accelerators, such as quaternaryammonium compounds; (7) wetting agents, such as, for example, acetylalcohol and glycerol monostearate; (8) absorbents, such as kaolin andbentonite clay; (9) lubricants, such as talc, calcium stearate,magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate,and mixtures thereof; and (10) colouring agents. In the case ofcapsules, tablets and pills, the pharmaceutical compositions may alsocomprise buffering agents. Solid compositions of a similar type may alsobe employed as fillers in soft and hard-filled gelatin capsules usingsuch excipients as lactose or milk sugars, as well as high molecularweight polyethylene glycols and the like.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared usingbinder (for example, gelatin or hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (for example,sodium starch glycolate or cross-linked sodium carboxymethyl cellulose),surface-active or dispersing agent. Molded tablets may be made bymolding in a suitable machine a mixture of the powdered activeingredient moistened with an inert liquid diluent.

The tablets, and other solid dosage forms of the pharmaceuticalcompositions described herein, such as dragees, capsules, pills andgranules, may optionally be scored or prepared with coatings and shells,such as enteric coatings and other coatings well known in thepharmaceutical-formulating art. They may also be formulated so as toprovide slow or controlled release of the active ingredient thereinusing, for example, hydroxypropylmethyl cellulose in varying proportionsto provide the desired release profile, other polymer matrices,liposomes and/or microspheres. They may be sterilized by, for example,filtration through a bacteria-retaining filter, or by incorporatingsterilizing agents in the form of sterile solid compositions which canbe dissolved in sterile water, or some other sterile injectable mediumimmediately before use. These compositions may also optionally containopacifying agents and may be of a composition that they release theactive ingredient(s) only, or preferentially, in a certain portion ofthe gastrointestinal tract, optionally, in a delayed manner. Examples ofembedding compositions which can be used include polymeric substancesand waxes. The active ingredient can also be in micro-encapsulated form,if appropriate, with one or more of the above-described excipients.

Liquid dosage forms for oral administration of the rifaximinpolymorph(s) include pharmaceutically-acceptable emulsions,microemulsions, solutions, suspensions, syrups and elixirs. In additionto the active ingredient, the liquid dosage forms may contain inertdiluents commonly used in the art, such as, for example, water or othersolvents, solubilizing agents and emulsifiers, such as ethyl alcohol,isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol,benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (inparticular, cottonseed, groundnut, corn, germ, olive, castor and sesameoils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fattyacid esters of sorbitan, and mixtures thereof.

In addition to inert diluents, the oral compositions can includeadjuvants such as wetting agents, emulsifying and suspending agents,sweetening, flavoring, coloring, perfuming and preservative agents.

Suspensions, in addition to the active rifaximin polymorph(s) maycontain suspending agents as, for example, ethoxylated isostearylalcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystallinecellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth,and mixtures thereof.

Pharmaceutical compositions for rectal or vaginal administration may bepresented as a suppository, which may be prepared by mixing one or morerifaximin polymorph(s) with one or more suitable nonirritatingexcipients or carriers comprising, for example, cocoa butter,polyethylene glycol, a suppository wax or a salicylate, and which issolid at room temperature, but liquid at body temperature and,therefore, will melt in the rectum or vaginal cavity and release theactive agent.

Compositions which are suitable for vaginal administration also includepessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining such carriers as are known in the art to be appropriate.

Dosage forms for the topical or transdermal administration of arifaximin polymorph(s) include powders, sprays, ointments, pastes,creams, lotions, gels, solutions, patches and inhalants. The activerifaximin polymorph(s) may be mixed under sterile conditions with apharmaceutically-acceptable carrier, and with any preservatives,buffers, or propellants which may be required.

Ointments, pastes, creams and gels may contain, in addition to rifaximinpolymorph(s), excipients, such as animal and vegetable fats, oils,waxes, paraffins, starch, tragacanth, cellulose derivatives,polyethylene glycols, silicones, bentonites, silicic acid, talc and zincoxide, or mixtures thereof.

Powders and sprays can contain, in addition to a rifaximin polymorph(s),excipients such as lactose, talc, silicic acid, aluminium hydroxide,calcium silicates and polyamide powder, or mixtures of these substances.Sprays can additionally contain customary propellants, such aschlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, suchas butane and propane.

The rifaximin polymorph(s) can be alternatively administered by aerosol.This is accomplished by preparing an aqueous aerosol, liposomalpreparation or solid particles containing the compound. A non-aqueous(e.g., fluorocarbon propellant) suspension could be used. Sonicnebulizers are preferred because they minimize exposing the agent toshear, which can result in degradation of the compound.

An aqueous aerosol is made, for example, by formulating an aqueoussolution or suspension of the agent together with conventionalpharmaceutically-acceptable carriers and stabilizers. The carriers andstabilizers vary with the requirements of the particular compound, buttypically include non-ionic surfactants (Tweens, Pluronics, orpolyethylene glycol), innocuous proteins like serum albumin, sorbitanesters, oleic acid, lecithin, amino acids such as glycine, buffers,salts, sugars or sugar alcohols. Aerosols generally are prepared fromisotonic solutions.

Transdermal patches have the added advantage of providing controlleddelivery of a rifaximin polymorph(s) to the body. Such dosage forms canbe made by dissolving or dispersing the agent in the proper medium.Absorption enhancers can also be used to increase the flux of the activeingredient across the skin. The rate of such flux can be controlled byeither providing a rate controlling membrane or dispersing the activeingredient in a polymer matrix or gel.

Ophthalmic formulations, eye ointments, powders, solutions and the like,are also contemplated as being within the scope of the invention.

Pharmaceutical compositions suitable for parenteral administration maycomprise one or more rifaximin polymorph(s) in combination with one ormore pharmaceutically-acceptable sterile isotonic aqueous or nonaqueoussolutions, dispersions, suspensions or emulsions, or sterile powderswhich may be reconstituted into sterile injectable solutions ordispersions just prior to use, which may contain antioxidants, buffers,bacteriostats, solutes which render the formulation isotonic with theblood of the intended recipient or suspending or thickening agents.

Examples of suitable aqueous and non-aqueous carriers which may beemployed in the pharmaceutical compositions include water, ethanol,polyols (such as glycerol, propylene glycol, polyethylene glycol, andthe like), and suitable mixtures thereof, vegetable oils, such as oliveoil, and injectable organic esters, such as ethyl oleate. Properfluidity can be maintained, for example, by the use of coatingmaterials, such as lecithin, by the maintenance of the required particlesize in the case of dispersions, and by the use of surfactants.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms may be ensured by the inclusion of variousantibacterial and antifungal agents, for example, paraben,chlorobutanol, phenol sorbic acid, and the like. It may also bedesirable to include isotonic agents, such as sugars, sodium chloride,and the like into the compositions. In addition, prolonged absorption ofthe injectable pharmaceutical form may be brought about by the inclusionof agents which delay absorption such as aluminum monostearate andgelatin.

In some cases, to prolong the effect of a drug, it is desirable to alterthe absorption of the drug. This may be accomplished by the use of aliquid suspension of crystalline, salt oramorphous material having poorwater solubility. The rate of absorption of the drug may then depend onits rate of dissolution which, in turn, may depend on crystal size andcrystalline form. Alternatively, delayed absorption of a drug form isaccomplished by dissolving or suspending the drug in an oil vehicle.

Injectable depot forms are made by forming microencapsule matrices ofrifaximin polymorph(s) in biodegradable polymers such aspolylactide-polyglycolide. Depending on the ratio of drug to polymer,and the nature of the particular polymer employed, the rate of drugrelease can be controlled. Examples of other biodegradable polymersinclude poly(orthoesters) and poly(anhydrides). Depot injectableformulations are also prepared by entrapping the drug in liposomes ormicroemulsions which are compatible with body tissue.

When the rifaximin polymorph(s) are administered as pharmaceuticals, tohumans and animals, they can be given per se or as a pharmaceuticalcomposition containing, for example, 0.1 to 99.5% (more preferably, 0.5to 90%) of active ingredient in combination with apharmaceutically-acceptable carrier.

Regardless of the route of administration selected, the rifaximinpolymorph(s), which may be used in a suitable hydrated form, and/or thepharmaceutical compositions of the present invention, are formulatedinto pharmaceutically-acceptable dosage forms by methods known to thoseof skill in the art.

Actual dosage levels and time course of administration of the activeingredients in the pharmaceutical compositions may be varied so as toobtain an amount of the active ingredient which is effective to achievethe desired therapeutic response for a particular subject, composition,and mode of administration, without being toxic to the subject. Anexemplary dose range is from 25 to 3000 mg per day.

A preferred dose of the rifaximin polymorph for the present invention isthe maximum that a subject can tolerate without developing serious sideeffects. Preferably, the rifaximin polymorph of the present invention isadministered at a concentration of about 1 mg to about 200 mg perkilogram of body weight, about 10-about 100 mg/kg or about 40 mg-about80 mg/kg of body weight. Ranges intermediate to the above-recited valuesare also intended to be part.

In combination therapy treatment, both the compounds of this inventionand the other drug agent(s) are administered to mammals (e.g., humans,male or female) by conventional methods. The agents may be administeredin a single dosage form or in separate dosage forms. Effective amountsof the other therapeutic agents are well known to those skilled in theart. However, it is well within the skilled artisan's purview todetermine the other therapeutic agent's optimal effective-amount range.In one embodiment in which another therapeutic agent is administered toan animal, the effective amount of the compound of this invention isless than its effective amount in case the other therapeutic agent isnot administered. In another embodiment, the effective amount of theconventional agent is less than its effective amount in case thecompound of this invention is not administered. In this way, undesiredside effects associated with high doses of either agent may beminimized. Other potential advantages (including without limitationimproved dosing regimens and/or reduced drug cost) will be apparent tothose skilled in the art.

In various embodiments, the therapies (e.g., prophylactic or therapeuticagents) are administered less than 5 minutes apart, less than 30 minutesapart, 1 hour apart, at about 1 hour apart, at about 1 to about 2 hoursapart, at about 2 hours to about 3 hours apart, at about 3 hours toabout 4 hours apart, at about 4 hours to about 5 hours apart, at about 5hours to about 6 hours apart, at about 6 hours to about 7 hours apart,at about 7 hours to about 8 hours apart, at about 8 hours to about 9hours apart, at about 9 hours to about 10 hours apart, at about 10 hoursto about 11 hours apart, at about 11 hours to about 12 hours apart, atabout 12 hours to 18 hours apart, 18 hours to 24 hours apart, 24 hoursto 36 hours apart, 36 hours to 48 hours apart, 48 hours to 52 hoursapart, 52 hours to 60 hours apart, 60 hours to 72 hours apart, 72 hoursto 84 hours apart, 84 hours to 96 hours apart, or 96 hours to 120 hourspart. In preferred embodiments, two or more therapies are administeredwithin the same subject's visit.

In certain embodiments, one or more compounds and one or more othertherapies (e.g., prophylactic or therapeutic agents) are cyclicallyadministered. Cycling therapy involves the administration of a firsttherapy (e.g., a first prophylactic or therapeutic agent) for a periodof time, followed by the administration of a second therapy (e.g., asecond prophylactic or therapeutic agent) for a period of time,optionally, followed by the administration of a third therapy (e.g.,prophylactic or therapeutic agent) for a period of time and so forth,and repeating this sequential administration, i.e., the cycle in orderto reduce the development of resistance to one of the therapies, toavoid or reduce the side effects of one of the therapies, and/or toimprove the efficacy of the therapies.

In certain embodiments, the administration of the same compounds may berepeated and the administrations may be separated by at least 1 day, 2days, 3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2 months, 75days, 3 months, or at least 6 months. In other embodiments, theadministration of the same therapy (e.g., prophylactic or therapeuticagent) other than a rifaximin polymorph may be repeated and theadministration may be separated by at least 1 day, 2 days, 3 days, 5days, 10 days, 15 days, 30 days, 45 days, 2 months, 75 days, 3 months,or at least 6 months.

Certain indications may require longer treatment times. For example,travelers' diarrhea treatment may only last from between about 12 hoursto about 72 hours, while a treatment for Crohn's disease may be frombetween about 1 day to about 3 months. A treatment for hepaticencephalopathy may be, for example, for the remainder of the subject'slife span. A treatment for IBS may be intermittent for weeks or monthsat a time or for the remainder of the subject's life.

Article of Manufacture

Another embodiment includes articles of manufacture that comprise, forexample, a container holding a pharmaceutical composition suitable fororal or topical administration of rifaximin in combination with printedlabeling instructions providing a discussion of when a particular dosageform should be administered with food and when it should be taken on anempty stomach. Exemplary dosage forms and administration protocols aredescribed infra. The composition will be contained in any suitablecontainer capable of holding and dispensing the dosage form and whichwill not significantly interact with the composition and will further bein physical relation with the appropriate labeling. The labelinginstructions will be consistent with the methods of treatment asdescribed hereinbefore. The labeling may be associated with thecontainer by any means that maintain a physical proximity of the two, byway of non-limiting example, they may both be contained in a packagingmaterial such as a box or plastic shrink wrap or may be associated withthe instructions being bonded to the container such as with glue thatdoes not obscure the labeling instructions or other bonding or holdingmeans.

Another aspect is an article of manufacture that comprises a containercontaining a pharmaceutical composition comprising rifaximin wherein thecontainer holds preferably rifaximin composition in unit dosage form andis associated with printed labeling instructions advising of thediffering absorption when the pharmaceutical composition is taken withand without food.

Packaged compositions are also provided, and may comprise atherapeutically effective amount of rifaximin. Rifaximin and apharmaceutically acceptable carrier or diluent, wherein the compositionis formulated for treating a subject suffering from or susceptible to abowel disorder, and packaged with instructions to treat a subjectsuffering from or susceptible to a bowel disorder.

Kits are also provided herein, for example, kits for treating a boweldisorder in a subject. The kits may contain, for example, one or more ofa Form ζ, Form η, Form α-dry, Form τ, Form β-1, Form β-2, Form ε-dry,mesylate Form or amorphous forms of rifaximin and instructions for use.The instructions for use may contain proscribing information, dosageinformation, storage information, and the like.

Packaged compositions are also provided, and may comprise atherapeutically effective amount of one or more of a polymorph ofrifaximin and a pharmaceutically acceptable carrier or diluent, whereinthe composition is formulated for treating a subject suffering from orsusceptible to a bowel disorder, and packaged with instructions to treata subject suffering from or susceptible to a bowel disorder.

Examples Materials

Rifaximin was stored in a dessicator at ambient temperature.

Characterization of Forms

Some of the hydrated, salt and amorphous forms of rifaximin, werecharacterized by one or more of XRPD, thermal analysis, FT-IR, FT-Raman,¹³C NMR. Dried materials obtained by vacuum drying or heating thehydrates were labeled “dry”. These materials exhibited XRPD patternsthat were shifted or contained one or two additional small peaks whencompared to the undried material.

Amorphous Material

Amorphous rifaximin (FIG. 1) was prepared by milling Form γ or Forms γ+ηat ambient temperature. Amorphous rifaximin was physically stable undervarious relative humidities and exhibited a high glass transitiontemperature onset of 199° C.

TG analysis of amorphous rifaximin demonstrated a 1.5% weight loss to100° C., accompanied by a broad endotherm at 78° C. in the DSC trace(FIG. 2), indicating the material contained residual solvent. A minorendotherm at 203° C. was also observed in the DSC trace. Cyclic DSC wasperformed to dry the sample and determine the T_(g), however the glasstransition temperature was not apparent from the data. Modulateddifferential scanning calorimetry showed the glass transition (T_(g))temperature onset to be approximately 199° C. (FIG. 3). Amorphousrifaximin was hygroscopic gaining 11.6% weight under 95% RH. The gainedweight was lost during the desorption cycle. The post moisture balanceXRPD pattern was amorphous.

The behavior of amorphous rifaximin under various relative humiditieswas also investigated. Amorphous material was stored under 43% RH for 5days, 58% RH for 8 days and 75% RH for 2 days. The material remainedamorphous by XRPD analysis.

Crystallization of rifaximin was conducted using water and varyingethanol/water ratios using a variety of techniques as disclosed herein.Additionally, drying studies were performed as well as stressing undervarious relative humidities.

Amorphous rifaximin was characterized by cyclic DSC and TG analyses:crash precipitation from ethyl acetate with heptane, lyophilization inp-dioxane:water 1:1, and fast evaporation from acetone. The cyclic DSCthermograms did not show evidence of a glass transition. A standard DSCtest was run on the amorphous sample generated by crash precipitationfrom ethyl acetate with heptane, and showed two broad endotherms atapproximately 79 and 204° C., indicative of likely desolvation followedby decomposition. Analysis by modulated DSC is pending for this sample.All the amorphous samples showed weight loss ranging from approximately5 to 6% from 25 to 200° C. by TG, indicating all three preparationslikely contain residual solvent.

Two amorphous preparations of Rifaximin (one from lyophilization inp-dioxane:water 1:1, the other from crash precipitation in ethyl acetatewith heptane, known as lyophilized amorphous rifaximin and crashamorphous rifaximin, respectively) were characterized by dynamic vaporsorption/desorption (DVS) analysis. Both samples were moderatelyhygroscopic, with a steady uptake of water (approximately 8% weight gainfor both samples) from 5 to 95% relative humidity. DVS curves for bothsamples showed hysteresis, as both lost more weight/water on desorptionthan they had gained on adsorption. Crystallization was not observed byeither post-DVS sample. Based on the data, relative humidity stressingstudies of the two amorphous materials at 40° C./75% RH are recommended.

Vapor stressing experiments were done on amorphous material from twopreparations:lyophilization from p-dioxane:water 1:1 and crashprecipitation from ethyl acetate with heptane. After 6 days, one sample(stressed with toluene) appeared microscopically birefringent,indicative of crystallization, but showed no peaks by XRPD. The majorityof the stressed samples appeared as clear red solutions after 6 days.Those solutions were placed in vials of antisolvent for vapor diffusion.Dry and wet milling experiments were conducted on amorphous materialsfrom the two preparations mentioned above. Amorphous materials wererecovered from the dry milling experiments.

Modulated DSC of x-ray amorphous rifaximin prepared from a crashprecipitation experiment in ethyl acetate with heptane showed noevidence of a glass transition temperature. A second modulated DSCexperiment on a sample of x-ray amorphous rifaximin from a vapor stressexperiment with water is pending. The presence of water in the samplecould possibly lower the glass transition temperature, potentiallymaking it detectable by modulated DSC.

Crystallization of amorphous rifaximin to Form β was observed for vapordiffusion experiments in methanol and tetrahydrofuran, both utilizingwater as an antisolvent.

TABLE 1 Amorphous Rifaximin Solvent Conditions Observation XRPD Resultacetone FE red glass, not amorphous, 2 birefringent halos p-lyophilization orange solids, not amorphous, 2 dioxane:H2O 1:1birefringent halos ethyl CP w/ bright orange, amorphous, 2 acetateheptane morphology halos unknown, not birefringent

TABLE 2 Characterization of Rifaximin, Amorphous Samples TechniqueAnalysis/Result XRPD amorphous, 2 halos cycling DSC^(a) no T_(g)observed TG^(b) 5.39% from 25-200° C. DVS^(c) 0.100% weight loss at 5%RH 8.364% eight gain from 5-95% RH 10.989% weight loss from 95-5% RHXRPD no peaks, possibly amorphous XRPD amorphous, 2 halos DSC^(a) broadendo 79, broad endo 204 cycling DSC^(a) no T_(g) observed modulated noT_(g) observed; broad endo 74 DSC^(a) TG^(b) 6.47% from 25-200° C.DVS^(d) 1.606% weight loss at 5% RH 7.843% weight gain from 5-95% RH9.172% weight loss from 95-5% RH XRPD no peaks, possibly amorphous XRPDamorphous, 2 halos cycling DSC^(a) no T_(g) observed TG^(b) 4.52% from25-200° C. XRPD amorphous ^(a)endo = endotherm, temperatures (° C.)reported are transition maxima. Temperatures are rounded to the nearestdegree. ^(b)weight loss (%) at a certain temperature; weight changes (%)are rounded to 2 decimal places; temperatures are rounded to the nearestdegree. ^(c)See 3436-54 for calculations. ^(d)See 3436-55 forcalculations.

TABLE 3 Stressing of Rifaximin, Amorphous Materials Solvent ConditionsObservations XRPD Result DCM VD w/ red, glassy solid, amorphous IPE, 11days not birefringent toluene VS, red, spherulites of amorphous RT, 6days needles, birefringent water VS, orange, amorphous RT, 15 daysaggregates and morphology unknown, not birefringent; dark read,agglomerate (very small amount), partially birefringent MEK VD w/ red,oily droplets amorphous IPE, 11 days in glassy solid, not birefringenta. Sample was analyzed by both Inel and Bruker XRPD to confirm result.

TABLE 4 Milling Experiments for Rifaximin, Amorphous Materials AmorphousXRPD Sample Source Conditions Observations Result lyophilization 10 min.at 30 Hz, bright orange, amorphous from p-dioxane: scraped sides, 10morphology water 1:1 min. at 30 Hz unknown, not birefringent CP fromEtOAc 10 min. at 30 Hz, bright orange, amorphous with heptane scrapedsides, 10 morphology min. at 30 Hz unknown, not birefringent

TABLE 5 Characterization of Rifaximin Amorphous Analysis ^(a) ConditionsResults XRPD Inel amorphous DSC Method A endotherm (major broad) 78° C.(25-250-10) endotherm (minor) 203° C. crimped pan DSC Cyclic DSC Glasstransition not determined MDSC Tg (glass transition) 199° C. TGA MethodA 1.5% from 21° C. to 100° C. (00-350-10) MB — 0.7% wt loss uponequilibration at 5% RH 11.6% wt gain from 5 to 95% RH 11.3% wt loss from95 to 5% RH ntbk ref. 2329-50 Post-MB Inel amorphous XRPD FT-IR 100%API, conforms to structure 256 scans FT-Raman 100% API, conforms tostructure 256 scans ^(a) XRPD = X-ray powder diffraction; DSC =differential scanning calorimetry; TGA = thermogravimetric analysis; MB= automated moisture sorption/desorption; FT-IR = Fourier transforminfrared spectroscopy; ¹H-NMR = solutions proton nuclear magneticspectroscopy; ¹³C-ssNMR = carbon-13 solid state nuclear magneticspectroscopy.

TABLE 6 Post-Moisture Sorption/Desorption Analysis Initial Form FinalForm α dry α dry Amorphous amorphous a. XRPD results are from postmoisture sorption/desorption analysis - sorption from 5% RH to 95% RH;desorption from 95% RH to 5% RH.

TABLE 7 Form amorphous Initial Form Conditions Final Form Amorphous PostMB amorphous Amorphous 43% RH, 5 days amorphous Amorphous 58% RH, 5 daysamorphous Amorphous 75% RH, 5 days amorphous γ ground at 30 Hz, 10 minamorphous (5 minute intervals x2) γ ground at 30 Hz, 30 min amorphous(15 minute intervalsx2) γ + η ground at 30 Hz, 45 min amorphous (15minute intervalsx3)

TABLE 8 Stressing Under Various Relative Humidities Initial FormConditions^(a) Observations XRPD Form amorphous 43% RH, 5 days orange;small irregular amorphous particles; no B&E amorphous 58% RH, 5 daysorange; small irregular amorphous particles; mostly no B&E 75% RH, 5days orange; small irregular amorphous particles; mostly no B&E ^(a)Allsamples stored at room temperature unless otherwise indicated; RH =relative humidity b. B = birefringence; E = extinction

Materials

Samples were stored in a dessicator. Solvents and other reagents usedwere purchased from commercial suppliers and used as received. Solventswere either HPLC or ACS grade.

Slow Evaporation (SE)

Solvent was added to weighed amounts of rifaximin in vials. Mixtureswere sonicated to achieve complete dissolution of solids. The solutionswere then filtered into clean vials. Solvents were slowly evaporated atambient conditions.

Crash Cool (CC)

A sample of rifaximin in ethanol/water 1/0.45 was prepared and passedthrough 0.2-μm nylon filter into a clean vial. The vial containing thesolution was then rapidly cooled by submersion in an ice bath forseveral seconds. Solids that precipitate were collected by filtrationand dried.

Slurry Experiments

Test solvents were added to rifaximin in vials such that excessundissolved solids were present in solutions. The mixtures were thanslurried on a shaker block or rotating wheel at subambient or roomtemperature.

Stressing Under Various Relative Humidities (RH)

A vial containing rifaximin was placed uncovered within a jar containingphosphorous pentoxide (P2O5) or a saturated salt solution in water. Thejar was sealed and stored at either ambient temperature or in an oven atelevated temperature.

Slow Cool (SC)

Saturated solutions of rifaximin were prepared by slurrying excesssolids in the test solvent at elevated temperature. The saturatedsolution was filtered while warm into a clean vial. The sample wasallowed to cool to room temperature, and then further cooled tosubambient temperature using a refrigerator, followed by a freezer.

Milling

A solid sample of rifaximin was charged to a milling container with amilling ball. Samples were milled for 5 or 15 minute intervals (2×5minutes, 2×15 minutes, and 3×15 minutes) at 30 Hz using a Retsch MM200mixer mill. Solids were scraped from the sides of the vial after eachinterval.

Instrumental Techniques X-Ray Powder Diffraction (XRPD) Shimadzu

X-ray powder diffraction (XRPD) analyses were performed using a ShimadzuXRD-6000 X-ray powder diffractometer using Cu Karadiation. Theinstrument is equipped with a long fine focus X-ray tube. The tubevoltage and amperage were set to 40 kV and 40 mA, respectively. Thedivergence and scattering slits were set at 1° and the receiving slitwas set at 0.15 mm. Diffracted radiation was detected by a NaIscintillation detector. A θ-2θ continuous scan at 3°/min (0.4 sec/0.02°step) from 2.5 to 40 ° 2θ was used. A silicon standard was analyzed tocheck the instrument alignment. Data were collected and analyzed usingXRD-6100/7000 v. 5.0. Samples were prepared for analysis by placing themin a sample holder.

Inel

X-ray powder diffraction (XRPD) analyses were performed using an InelXRG-3000 diffractometer equipped with a CPS (Curved Position Sensitive)detector with a 28 range of 120°. Real time data were collected usingCu—Kα radiation starting at approximately 4 ° 2θ at a resolution of 0.03° 2θ. The tube voltage and amperage were set to 40 kV and 30 mA,respectively. The monochromator slit was set at 5 mm by 160 μm. Thepattern is displayed from 2.5-40 ° 2θ. Samples were prepared foranalysis by packing them into thin-walled glass capillaries. Eachcapillary was mounted onto a goniometer head that is motorized to permitspinning of the capillary during data acquisition. The samples wereanalyzed for 300 sec. Instrument calibration was performed using asilicon reference standard.

Variable Temperature XRPD (VT-XRPD)

Variable-temperature XRPD (VT-XRPD) was performed on a Shimadzu XRD-6000X-ray powder diffractometer equipped with an Anton Paar HTK 1200 hightemperature stage. The sample was packed in a ceramic holder andanalyzed from 2.5 to 40 ° 2θ at 3°/min (0.4 sec/0.02° step). The heatingrate was 10° C./min. A silicon standard was analyzed to check theinstrument alignment. Temperature calibration was performed usingvanillin and sulfapyridine standards. Data were collected and analyzedusing XRD-6000 v. 4.1.

Variable Relative Humidity XRPD (VRH-XRPD)

VRH-XRPD was performed on a Shimadzu XRD-6000 X-ray powderdiffractometer equipped with a relative humidity generator, RH-200. Thisanalysis is non-cGMP. The sample was packed in a ceramic holder andanalyzed from 2.5-40 ° 2θ at 3°/min (0.4 sec/0.02° step) atapproximately 32° C. The RH profile for the chamber is specified in thetables. XRPD patterns were collected during this time frame every 15minutes for two hours. A data logger (SN#05012010) was used to measurethe relative humidity in the chamber (see DATA section pages 57-60). Asilicon standard was analyzed to check the XRPD instrument alignment.XRPD Data were collected and analyzed using XRD-6100/7000 v.5.0.

Reference XRPD Patterns

Reference XRPD patterns were obtained from US or European Patents orPatent Applications and converted to electronic files using UN-SCAN-ITversion 6.0 (non-cGMP).

Optical Microscopy

Optical microscopy was performed using a Leica MZ12.5 stereomicroscope.Various objectives typically ranging from 0.8-4× were used withcrossed-polarized light to view samples. Samples were viewed in situ.

Thermal Analyses

Differential Scanning calorimetry (DSC)

Differential scanning calorimetry (DSC) was performed using a TAInstruments differential scanning calorimeter 2920. The sample wasplaced into an aluminum DSC pan, and the weight accurately recorded. Thepan was covered with a lid and then crimped or left uncrimped. Thesample cell was equilibrated at 25° C. and heated under a nitrogen purgeat a rate of 10° C./min, up to a final temperature of 250 or 350° C.Indium metal was used as the calibration standard. Reported temperaturesare at the transition maxima.

Method A: 25-250-10: initial equilibration at 25° C., heated to 250° C.at 10° C./min

Method B: 25-350-10: initial equilibration at 25° C., heated to 350° C.at 10° C./min

Cyclic Differential Scanning calorimetry

Cyclic DSC was performed using a TA Instruments 2920 differentialscanning calorimeter. The sample was placed into a hermetically sealedDSC pan, and the weight accurately recorded. The pan was covered with alid containing a laser pinhole. The method was as follows:

1. Equilibrate at −50° C.

2. Ramp 20° C./min to 80° C.

3. Isothermal at 80° C. for 1 min

4. Equilibrate at −50° C.

5. Ramp 20° C./min to 220° C.

Indium metal was used as the calibration standard. Reported temperatureis at the transition maxima.Modulated Differential Scanning calorimetry (MDSC)

Modulated differential scanning calorimetry (MDSC) data were obtained ona TA Instruments differential scanning calorimeter 2920 equipped with arefrigerated cooling system (RCS). The sample was placed into analuminum DSC pan, and the weight accurately recorded. The pan wascovered with a lid perforated with a laser pinhole to allow for pressurerelease, and then hermetically sealed. MDSC data were obtained using amodulation amplitude of +/−0.8° C. and a 60 second period with anunderlying heating rate of 1° C./min from 25-225° C. The temperature andthe heat capacity were calibrated using indium metal and sapphire as thecalibration standards, respectively. The reported glass transitiontemperatures are obtained from the half-height/inflection of the stepchange in the reversible heat flow versus temperature curve.

Thermogravimetric (TG) Analyses

Thermogravimetric (TG) analyses were performed using a TA Instruments2950 thermogravimetric analyzer. Each sample was placed in an aluminumsample pan and inserted into the TG furnace. The furnace was firstequilibrated at 25° C. or started directly from ambient temperature,then heated under nitrogen at a rate of 10° C./min, up to a finaltemperature of 350° C. Nickel and Alumel™ were used as the calibrationstandards. Methods for specific samples are referred to as summarizedbelow

-   -   Method A: 00-350-10: no initial equilibration; analysis started        directly from ambient, sample heated to 350° C. at 10° C./min    -   Method B: 25-350-10: initial equilibration at 25° C., sample        heated to 350° C. at 10° C./min    -   Method C: 00-300-10: no initial equilibration; analysis started        directly from ambient, sample heated to 300° C. at 10° C./min

Spectroscopy Fourier Transform Infrared (FT-IR)

The IR spectra were acquired on a Magna-IR 860® Fourier transforminfrared (FT-IR) spectrophotometer (Thermo Nicolet) equipped with anEver-Glo mid/far IR source, an extended range potassium bromide (KBr)beamsplitter, and a deuterated triglycine sulfate (DTGS) detector. Anattenuated total reflectance (ATR) accessory (the Thunderdome™, ThermoSpectra-Tech), with a germanium (Ge) crystal was used for dataacquisition. The spectra represent 256 co-added scans collected at aspectral resolution of 4 cm⁻¹. A background data set was acquired with aclean Ge crystal. A Log 1/R (R=reflectance) spectrum was acquired bytaking a ratio of these two data sets against each other. Wavelengthcalibration was performed using polystyrene.

Fourier Transform Raman (FT-Raman)

FT-Raman spectra were acquired on a Raman accessory module interfaced toa Magna 860® Fourier transform infrared (FT-IR) spectrophotometer(Thermo Nicolet). This module uses an excitation wavelength of 1064 nmand an indium gallium arsenide (InGaAs) detector. Approximately 0.6-2.0W of Nd:YVO₄ laser power was used to irradiate the sample. The sampleswere prepared for analysis by placing the material in a glass tube andpositioning the tube in a gold-coated tube holder in the accessory Atotal of 256 or 1024 sample scans were collected from 98-3600 cm⁻¹ at aspectral resolution of 4 cm⁻¹, using Happ-Genzel apodization. Wavelengthcalibration was performed using sulfur and cyclohexane.

Automated Moisture Sorption/Desorption

Moisture sorption/desorption data were collected on a VTI SGA-100 VaporSorption Analyzer. Sorption and desorption data were collected over arange of 5% to 95% relative humidity (RH) at 10% RH intervals under anitrogen purge. Samples were not dried prior to analysis. Equilibriumcriteria used for analysis were less than 0.0100% weight change in 5minutes, with a maximum equilibration time of 3 hours if the weightcriterion was not met. Data were not corrected for the initial moisturecontent of the samples. NaCl and PVP were used as calibration standards.

Solid State ¹³C Nuclear Magnetic Resonance (NMR)

Samples were prepared for solid-state NMR spectroscopy by packing theminto 4 mm PENCIL type zirconia rotors. The specific acquisitionparameters are listed on the plot of the first full spectrum of eachsample in the data section.

XRPD Data for Rifaximin Forms

High resolution XRPD data were collected on rifaximin forms ζ and η toidentify peak positions as well as aid in indexing the patterns. Form ζwas successfully indexed using this data. Due to the disorder inherentin Form η attempts to index the XRPD pattern were unsuccessful. The XRPDpeak list for rifaximin Form ζ was generated using the results of theindexed pattern. XRPD peak lists for rifaximin Form η and X-rayamorphous were generated using PatternMatch, an SSCI software package.The diffractograms were compared to the software generated peak list toensure peaks selected were real. Broad and/or low intensity peaks aswell as peaks beyond 20 ° 2θ were not included in the peak positiontables.

Preparation Methods for Select Rifaximin Forms

Rifaximin X-ray Amorphous

Rifaximin (50 mg, Form γ+η) was ground for three 15 minute cycles in agrinding jar at 30 Hz (total 45 minutes). Solids were scraped from sidesof the jar after each cycle. Orange fragments were recovered and storedrefrigerated, in a dessicator prior to analysis. (FIG. 4).

X-Ray Powder Diffraction (XRPD) Inel XRG-3000 Diffractometer

X-ray powder diffraction (XRPD) analyses were performed using an InelXRG-3000 diffractometer equipped with a CPS (Curved Position Sensitive)detector with a 20 range of 120°. Real time data were collected usingCu—K α radiation. The tube voltage and amperage were set to 40 kV and 30mA, respectively. The monochromator slit was set at 1-5 mm by 160 μm.The patterns are displayed from 2.5-40 ° 2 θ. Samples were prepared foranalysis by packing them into thin-walled glass capillaries. Eachcapillary was mounted onto a goniometer head that is motorized to permitspinning of the capillary during data acquisition. The samples wereanalyzed for 300 seconds. Instrument calibration was performed using asilicon reference standard.

PANalytical X'Pert Pro Diffractometer

Samples were also analyzed using a PANalytical X'Pert Prodiffractometer. The specimen was analyzed using Cu radiation producedusing an Optix long fine-focus source. An elliptically graded multilayermirror was used to focus the Cu K α X-rays of the source through thespecimen and onto the detector. The specimen was sandwiched between3-micron thick films, analyzed in transmission geometry, and rotated tooptimize orientation statistics. A beam-stop and a helium purge wereused to minimize the background generated by air scattering. Sollerslits were used for the incident and diffracted beams to minimize axialdivergence. Diffraction patterns were collected using a scanningposition-sensitive detector (X'Celerator) located 240 mm from thespecimen. The data-acquisition parameters of each diffraction patternare displayed above the image of each pattern in appendix data section.Prior to the analysis a silicon specimen (NIST standard referencematerial 640c) was analyzed to verify the position of the silicon 111peak.

TABLE 9 XRPD Range of Amorphous halo of Rifaximin Form X-ray AmorphousPosition (°2θ) 5.1-10.1 (amorphous halo range) 7.3 (approximate halomaximum) 11.3-17.8 (amorphous halo range) 15.8 (approximate halomaximum)

INCORPORATION BY REFERENCE

The contents of all references, patents, pending patent applications andpublished patents, cited throughout this application are herebyexpressly incorporated by reference.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

1. Form amorphous of rifaximin.
 2. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an X-ray powder diffraction pattern having characteristic peaks expressed in degrees 2θ (+/−0.20 degree θ) at 7.3 (approximate halo maximum), 11.3-17.8 (amorphous halo range), and 15.8 (approximate halo maximum) degrees 2-θ.
 3. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an X-ray powder diffraction pattern having characteristic peaks expressed in degrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 11.3-17.8 (amorphous halo range), and 15.8 (approximate halo maximum) degrees 2-θ.
 4. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an X-ray powder diffraction pattern having characteristic peaks expressed in degrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 7.3 (approximate halo maximum), and 11.3-17.8 (amorphous halo range) degrees 2-θ.
 5. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an X-ray powder diffraction pattern having characteristic peaks expressed in degrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 7.3 (approximate halo maximum), and 15.8 (approximate halo maximum) degrees 2-θ.
 6. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an X-ray powder diffraction pattern having characteristic peaks expressed in degrees 2θ (+/−0.20 degree θ) at 5.1-10.1 (amorphous halo range), 7.3 (approximate halo maximum), 11.3-17.8 (amorphous halo range), 15.8 (approximate halo maximum) degrees 2-θ.
 7. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits Thermogravimetric analyses (TGA) of a 1.5% weight loss at 100° C.
 8. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits Differential Scanning calorimetry (DSC) of a broad endotherm at about 78° C. and a minor endotherm at 203° C.
 9. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits Modulated Differential Scanning calorimetry (MDSC) having a glass transition (Tg) temperature onset to be about 199° C.
 10. A compound according to claim 1, wherein amorphous form of rifaximin contains less than 5% by weight total impurities.
 11. A compound according to claim 1, wherein the amorphous form of rifaximin is at least 50% pure, or at least 75% pure, or at least 80% pure, or at least 90% pure, or at least 95% pure, or at least 98% pure.
 12. A compound according to claim 1, wherein amorphous forms of rifaximin further comprise a pharmaceutically acceptable carrier.
 13. A compound according to claim 1, wherein forms of rifaximin of are formulated as coated or uncoated tablets, hard or soft gelatin capsules, sugar-coated pills, lozenges, wafer sheets, pellets or powders in sealed packets. 14-20. (canceled)
 21. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an XRPD pattern substantially similar to FIG.
 1. 22. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a TGA and a DSC substantially similar to FIG.
 2. 23. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits an XRPD pattern substantially similar to FIG.
 4. 24. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a DSC substantially similar to FIG.
 6. 25. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a cycling DSC substantially similar to FIG.
 7. 26. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a TG substantially similar to FIG.
 8. 27. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a cycling DSC substantially similar to FIG.
 10. 28. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a TG substantially similar to FIG.
 11. 29. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a cycling DSC substantially similar to FIG.
 13. 30. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a TG substantially similar to FIG.
 14. 31. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a modulated DSC substantially similar to FIG.
 15. 32. A compound according to claim 1, wherein the amorphous form of rifaximin exhibits a modulated DSC substantially similar to FIG.
 16. 